The present invention relates to slab-type optical devices, and more particularly to a light beam splitter for dividing a light beam in two or conversely for superposing two light beams and to application devices thereof.
Optical integrated circuit techniques are indispensable to the commercial use of optical communication systems and optical information processing systems. These techniques include a slab-type optical circuit technique which is an especially important basic technique. Many attempts have been made to fabricate optical circuits on substrate plates. A light beam splitter is one of such devices. A directional coupler has been used as a device which performs the function of the light beam splitter in a slab-type optical circuit. The coupler comprises two parallel waveguides formed on a substrate and arranged close to each other for transferring an optical power between the waveguides by coupling. When the distance between the waveguides, i.e. the degree of coupling, and the length of coupling are suitably determined, the coupler can perform the same function as a beam splitter. For this purpose, however, there is a need to accurately determine suitable values for the three parameters of the configuration of the waveguides, the spacing therebetween and the length of coupling.